Man, I couldn't tell you what is the best. But I can say that it is possible to do in CFX. The problem is the coupling between the chemistry and multiphase. If you get the insight you get the right results.

CFX has been known for its strength in multiphase and chemistry for a while. There have been postings earlier abount CFX vs. other codes (Star-CD in particular). In CFX-4.4 moreover you have not only a large panel of models which are pre-available, but you can also code yourself quite a lot more. As Ribeiro said, what is often more importatnt is to get the set up (i.e. understand how to model the reaction) right. In CFX-5.5 a lot more model are being added and the sover is fully coupled which makes simulation even more robust.